Area Forecast Discussion
Issued by NWS Charleston, SC

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412
FXUS62 KCHS 060556
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1256 AM EST SAT FEB 6 2016

.SYNOPSIS...
INLAND HIGH PRESSURE WILL PREVAIL TONIGHT. A COASTAL TROUGH
WILL DEVELOP OFFSHORE AND STRENGTHEN SATURDAY. LOW PRESSURE WILL
TRACK NORTH AND DEEPEN OFF THE SOUTHEAST COAST SATURDAY NIGHT
THROUGH SUNDAY....THEN WILL MOVE AWAY TOWARD THE NORTHEAST SUNDAY
NIGHT. A COLD FRONT WILL CROSS THE AREA MONDAY. THEN...A DEEP
TROUGH WILL REMAIN IN PLACE THROUGH THE MIDDLE OF NEXT
WEEK...BRINGING UNSEASONABLY COOL CONDITIONS TO THE AREA.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
ONLY MINOR TWEAKS TO THE FORECAST...MAINLY TO ACCOUNT FOR SOME
STRATOCUMULUS TO ADVECT ONSHORE OF EXTREME SE COASTAL GA AND TO
OPEN A LITTLE GREATER RANGE FROM NW TIER TO THE COAST IN REGARDS
TO TEMPS. ON AVERAGE LOOKING FOR 29-33 MOST INLAND
COMMUNITIES...36-40 ALONG THE COAST AND IN DOWNTOWN CHARLESTON.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/...
THIS FORECAST PERIOD INCLUDES A PARTICULARLY CHALLENGING
PRECIPITATION EVENT...AND MOST ATTENTION FOCUSES ON THE POTENTIAL
FOR A PERIOD OF WET SNOW LATE SATURDAY NIGHT INTO SUNDAY MORNING.
LOW PRESSURE WILL BE TRACKING NORTH/NORTHEAST AND DEEPENING RAPIDLY
OFF THE SOUTHEAST COAST...WHILE AN IMPRESSIVE UPPER LOW WILL
TRAVERSE SOUTHERN COUNTIES OF THE FORECAST AREA. AS THE UPPER LOW
TRENDS TOWARD A NEGATIVE TILT...STRONG FORCING FOR ASCENT WILL
DEVELOP ACROSS THE REGION. INITIALLY...THE RESPONSE WILL INCLUDE AN
EXPANSION DEEP LAYERED MOISTURE AND RAIN ACROSS MUCH OF THE FORECAST
AREA AS SATURDAY NIGHT PROGRESSES. THEN...LATE SATURDAY NIGHT INTO
SUNDAY MORNING COLD ADVECTION WILL PUSH TOWARD THE COAST IN CONCERT
WITH DYNAMIC COOLING. THE BIG QUESTION IS WHETHER SUFFICIENT COOLING
WILL OCCUR WHILE DEEP COMMA CLOUD MOISTURE REMAINS OVER THE REGION
TO SUPPORT NON-LIQUID PRECIPITATION. 12Z MODELS HAVE CERTAINLY
TRENDED FARTHER WEST WITH A LONGER DURATION COMMA FEATURE NORTH OF
THE UPPER LOW...AND WE HAVE ACCORDINGLY RAISED POPS TO CATEGORICAL
MOST AREAS EXCEPT FAR INLAND SATURDAY NIGHT...FOLLOWED BY A LONGER
PERIOD OF PRECIPITATION SUNDAY. HOWEVER...MODELS HAVE OFFERED AN
UNEVEN THERMAL EVOLUTION...AND MUCH OF THE FORECAST UNCERTAINTY
HINGES ON THE UNCERTAIN DEGREE OF COOLING. THE MOST LIKELY SCENARIO
SUGGESTS THAT RAIN WILL MIX WITH OR CHANGE TO A PERIOD OF WET SNOW
LATE SATURDAY NIGHT INTO SUNDAY MORNING...WITH TEMPERATURES ABOVE
FREEZING PREVENTING ANY SIGNIFICANT ACCUMULATION/IMPACTS. HOWEVER...
IN A WORST CASE BUT LESS LIKELY SCENARIO...STRONG FORCING FOR ASCENT
WILL SUPPORT LOCAL CONVECTIVE ENHANCEMENT...AND RAIN/MIXED
PRECIPITATION COULD GIVE WAY TO LOCALIZED/HEAVIER BURSTS OF WET SNOW
WHICH COULD BRIEFLY BUT QUICKLY ACCUMULATE ON ROADS...TREE LIMBS AND
POWER LINES. WHILE THE PAST COUPLE RUNS OF THE NAM SUPPORT A
SIGNIFICANT SNOW EVENT...THIS MODEL APPEARS TO CONVERT TOO MUCH RAIN
TO SNOW AND COULD WELL BE PLACING THE CRITICAL COMMA HEAD
MOISTURE/CRITICAL TEMPS FOR SNOW MUCH TOO FAR INLAND. AS OF LATE
FRIDAY AFTERNOON...THE PROBABILITY FOR THE WORST CASE SCENARIO
REMAINS TOO LOW TO JUSTIFY A WINTER STORM WATCH...BUT WILL ADDRESS
THE WITHIN THE HAZARDOUS WEATHER OUTLOOK.

BACKING UP IN TIME...SATURDAY WILL TURN OUT MOSTLY CLOUDY WITH BELOW-
NORMAL HIGH TEMPS IN THE 50S. WITH THE POSSIBLE EXCEPTION OF SOUTH
COASTAL COUNTIES...MOST AREAS SHOULD REMAIN RAIN-FREE UNTIL AFTER
DARK.

LOOKING AHEAD...EXPECT A CHILLY AND DRY NIGHT SUNDAY
NIGHT...FOLLOWED BY A COLD FROPA MONDAY. MOISTURE APPEARS TOO MEAGER
TO SUPPORT ANY MEASURABLE PRECIPITATION. TEMPERATURES 55-60F SHOULD
BE COMMON.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
OVERALL THE LONG TERM PERIOD LOOKS RATHER STEADY STATE AND COOL. THE
DEEP AND COLD TROUGH IN THE MID/UPPER LEVELS WILL PERSIST AND EVEN
GET REINFORCED BY ADDITIONAL ENERGY DIVING OUT OF THE NORTHERN
PLAINS INTO MID WEEK. THIS SET UP WILL KEEP TEMPERATURES COOL AND
WELL BELOW NORMAL WITH BREEZY CONDITIONS EACH AFTERNOON. HIGH
PRESSURE WILL SETTLE INTO THE REGION FROM THE CENTRAL CONUS BY ABOUT
THURSDAY. FOR MUCH OF THE PERIOD HIGHS WILL STRUGGLE TO GET OUT OF
THE 40S WITH OVERNIGHT LOWS INTO THE 20S AWAY FROM THE COAST.
ALSO...THERE ARE NO SIGNIFICANT OPPORTUNITIES FOR RAIN.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR AT KSAV AND KCHS OVERNIGHT AND SATURDAY...ALTHOUGH BKN-OVC
CEILINGS WILL DEVELOP IN THE MORNING AS THEY ARRIVE FROM OFF THE
ATLANTIC. LIGHT RAINS WILL OCCUR IN THE AFTERNOON AND CONTINUE
INTO TONIGHT IN RESPONSE TO A COASTAL TROUGH OFFSHORE AND ENERGY
ALOFT. THIS EVENTUALLY LEADS TO LOW-END VFR CONDITIONS AT KCHS AND
MVFR CONDITIONS AT KSAV.

EXTENDED AVIATION OUTLOOK...THERE WILL BE A CHANCE FOR RESTRICTED
CEILINGS SATURDAY NIGHT INTO SUNDAY MORNING. OTHERWISE VFR
CONDITIONS WILL PREVAIL.

&&

.MARINE...
TONIGHT...HIGH PRESSURE WILL BUILD ACROSS THE SOUTHEAST U.S. WITH
NE WINDS AS HIGH AS 15-20 KT IN RESPONSE TO THE SURFACE PRESSURE
GRADIENT INCREASING BETWEEN THE HIGH AND A COASTAL TROUGH
BEGINNING TO FORM. SEAS WILL BE 3-4 FT WITHIN 20 NM AND 4-6 FT
ACROSS THE OUTER GEORGIA WATERS. THE SMALL CRAFT ADVISORY WILL
REMAIN UP FOR THE OUTER GEORGIA WATERS.

SATURDAY THROUGH WEDNESDAY...DUE TO THE DEEPENING LOW PRESSURE
OFF THE SOUTHEAST COAST...RAISED A GALE WATCH FOR AMZ374 SATURDAY
NIGHT THROUGH SUNDAY...AND THERE EXISTS A LOW PROBABILITY FOR
GALES TO SPREAD INTO NEAR SHORE WATERS DURING THIS TIME.
OTHERWISE...ELEVATED WINDS/SEAS AND SMALL CRAFT ADVISORY
CONDITIONS WILL REMAIN COMMON THROUGH THIS PERIOD. ANOTHER PERIOD
OF GALES IS POSSIBLE IN THE WAKE OF A COLD FRONT MONDAY
NIGHT/TUESDAY...ESPECIALLY BEYOND 20 NM.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...GALE WATCH FROM THIS EVENING THROUGH SUNDAY EVENING FOR AMZ374.
     SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR AMZ374.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...BSH
AVIATION...
MARINE...



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